1. Field of the Invention
The present invention relates to an internal combustion engine control device that controls a fuel injection mode and an intake air condition.
2. Description of Related Art
Conventionally, there has been proposed a control device that senses pressure in a combustion chamber (cylinder pressure) with a cylinder pressure sensor and senses a combustion characteristic of the cylinder based on the cylinder pressure sensing value, the control device controlling an internal combustion engine in accordance with the sensed combustion characteristic. For example, a control device for a diesel engine described in Patent document 1 (JP-A-2005-351161) calculates an energy generation rate (a heat release rate) caused by combustion of fuel in a combustion chamber based on the cylinder pressure sensing value and detects actual ignition timing as a combustion characteristic by using the calculated heat release rate.
The control device corrects an injection mode as follows in accordance with a combustion variation such as a deviation of the detected ignition timing from desired ignition timing. That is, in the case of a multi-stage injection (i.e., multi-injection) of performing the injection multiple times during one combustion cycle, the control device corrects a main injection start timing, a pilot injection quantity or the like. In the case of a single-stage injection, the control device corrects an injection start timing.
However, only information after the combustion is known from the cylinder pressure sensing value. Therefore, it is impossible to determine which of the injection mode and the intake air condition is the cause of the combustion variation sensed from the cylinder pressure sensing value. In the above-described conventional control, only the injection mode is corrected irrespective of which is the cause when the combustion variation is detected. Therefore, only the injection mode such as the injection start timing is corrected even when the combustion variation is caused by a variation in the intake air condition such as an EGR quantity (exhaust gas recirculation quantity) or supercharging pressure. Therefore, it cannot be said that the injection mode and the intake air condition are fully optimized. There exists a room for improvement.